1. Field of the Invention
The present invention relates to an audio signal processing apparatus and method, and more particularly, to an audio signal processing apparatus and method that may supply a suitable power to an amplifier in accordance with an output level of an audio signal so as to perform the amplification with high efficiency from a small output level to a large output level.
2. Background of the Invention
An audio signal processing apparatus applicable to an audio apparatus using, audio disks, such as a mini-disk (MD),a compact disk (CD),or a digital versatile disk (DVD) provides an audio power amplifier (PA) for amplifying and driving an audio speaker and a power supplier in order to supply a power corresponding to a maximum output value of the audio signal.
Usually, a power supplier for an audio apparatus is designed so it can supply the maximum power to an amplifier when the audio output volume is maximized, while maintaining a constant voltage. For instance, Japanese Patent Application Publication 2001-77634 discloses such an audio signal processing apparatus in that a power supplier can supply maximum voltages +Vdd (hereinafter referred to be as “+B”) and −Vdd (hereinafter referred to be as “−B”) at a maximized volume time. After modulating the volume of the audio input signal, the amplified audio signal is outputted through an output terminal. The audio power amplifier in this audio signal processing apparatus operates as an analog amplifier of class “A” amplification, class “B” amplification or class “AB” amplification at the maximum voltages +Vdd and −Vdd.
However, the conventional audio signal processing apparatus supplies the maximum voltages +Vdd and −Vdd to the audio power amplifier even when the volume of the audio output is rather a small level or a middle level. Thus, the audio signal processing apparatus always operates at the maximum voltages +Vdd and −Vdd, while a power load efficiency (ηadd) is approximately several percent (%) reduced from the audio maximum output time during a normal calculation time. Since the conventional audio signal processing apparatus always generates useless power at a normal calculation time, a mean power load efficiency (ηadd) is extremely reduced. Accordingly, the conventional audio signal processing apparatus has problems and defects for supplying power to the amplifier.